If $x \diamond y = 3x-y$ and $x \boxdot y = x+6y$, find $-3 \diamond (5 \boxdot -1)$.
Solution: First, find $5 \boxdot -1$ $ 5 \boxdot -1 = 5+(6)(-1)$ $ \hphantom{5 \boxdot -1} = -1$ Now, find $-3 \diamond -1$ $ -3 \diamond -1 = (3)(-3)-(-1)$ $ \hphantom{-3 \diamond -1} = -8$.